Preheat the oven to 350°F. Spray 9-by-13 inch square baking pan with nonstick cooking spray. Put a long piece of parchment paper in the bottom of the pan pushing it into corners and letting the parchment extend up the two short sides of the pan and overhang slightly on both ends. Fit second sheet of parchment paper in pan in same manner, perpendicular to first sheet. Spray sheets with nonstick cooking spray.

Spread the almonds (3/4 cup) onto a baking sheet and place in preheated oven 8-10 minutes until fragrant. Shake the baking sheet halfway through baking so the nuts will toast evenly. Remove nuts from oven and set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat together the butter and sugar on medium speed until light, about 2 minutes. Beat in the egg yolk, vanilla, and salt. On low speed, gradually beat in the flour just until mixed. The dough will be stiff. Pat the dough evenly over the bottom of the baking pan.

Bake in the center of the oven until pale gold on top, about 20 minutes.

Remove the pan from the oven and scatter the chocolate pieces evenly over the crust. Return the pan to the oven for 1 minute. Remove the pan again and, using a knife, spread the chocolate evenly over the crust. Sprinkle evenly with the almonds and toffee bits.

Let cool completely in the pan on a wire rack. Remove bars from pan using parchment handles and transfer to cutting board. Cut into bars.